1. Field of the Invention
The present invention relates to a sterilant system and method for sterilising surfaces.
2. Description of the Prior Art
Two-part sterilising solutions are used in applications where the active sterilising ingredient is unstable over time. The solution is therefore prepared in situ shortly before it is to be used. A particularly important sterilising agent is chlorine dioxide (ClO2), which may be formed from mixtures of various reagents including: chlorite and acid; chlorate, peroxide and acid; and chlorite, hypochlorite, and a suitable buffer. Chlorine dioxide has excellent sterilising and bactericidal properties, and oral ingestion in man and animals has been shown to be relatively safe.
ClO2 gas is a respiratory and eye irritant so its concentration in air needs to be controlled at safe levels. The occupational exposure standard limit (OES) in the UK is set at 0.3 ppm (0.9 mg/m3) as a 15 minute short term exposure limit (STEL) and at 0.1 ppm for an 8 hour time-weighted average (TWA). In the USA, OSHA, NIOSH and ACGIH all set the limit at 0.1 ppm for long-term exposure.
ClO2 sterilising solutions have many uses, particularly in hospital and medical environments where medical equipment and apparatus such as isolation tents need to be sterilised to reduce risks of cross-infection. The cleaning of endoscopes and other medical equipment with suitable chlorine dioxide solutions is known from earlier patents in the name of the present inventor, for example, European Patent Number 0 785 719 and U.S. Pat. Nos. 5,696,046 and 6,007,772, the contents of which are hereby incorporated by reference.
It is not always convenient to mix up batches of solutions for use in sterilising equipment. For wiping down (rather than thoroughly cleaning inside and out) of endoscopes and probes, wipes of alcohol, general-purpose detergent, or soapy water are generally used, but these are not as effective as chlorine dioxide. It is desirable to be able readily to make up small quantities of two-component sterilising agents when desired and to be able to make such agents up in a form in which they may be readily handled for a particular application and which is compatible with OES limits.